Systems And Methods For Concentrating Waste Water Fluids

ABSTRACT

A method and apparatus for processing waste water generated during oilfield drilling operations with a mobile processing unit utilizing heat energy sourced from burning hydrocarbon fuel directly and/or capturing and using the exhaust heat energy generated by burning hydrocarbons in engines such as diesel engines in order to vaporize a dominant mass of the aqueous phase of the waste water while clarifying the heat source combustion gasses. The water vapor generated by the vaporization process may be discharged directly to the atmosphere or alternately condensed and captured for use as potable water. The residual waste water is thereby concentrated and the cost to dispose of the waste water is greatly reduced.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of pending U.S. applicationSer. No. 13/420,314, filed on Mar. 14, 2012, which is a continuation ofInternational Patent Application No. PCT/CA2010/001440, filed on Sep.17, 2010, which claims the benefit under 35 U.S.C. §119 (e) of U.S.Provisional Patent Application No. 61/333,864, filed on May 12, 2010 andof U.S. Provisional Patent Application No. 61/243,738, filed on Sep. 18,2009. The content of all prior applications is incorporated herein byreference.

TECHNICAL FIELD

The invention relates to a method and apparatus for processing wastewater generated during oilfield drilling operations with a mobileprocessing unit utilizing heat energy sourced from burning hydrocarbonfuel directly and/or capturing and using the exhaust heat energygenerated by burning hydrocarbons in engines such as diesel engines inorder to vaporize a dominant mass of the aqueous phase of the wastewater while clarifying the heat source combustion gasses. The watervapor generated by the vaporization process may be discharged directlyto the atmosphere or alternately condensed and captured for use aspotable water. The residual waste water is thereby concentrated and thecost to dispose of the waste water is greatly reduced.

BACKGROUND

There are many examples where evaporation is used to reduce the liquidphase of water solutions containing contaminants for the purpose ofconcentrating the contaminants for disposal. Often referred to asthermal separation or thermal concentration processes, these processesgenerally begin with a liquid and end up with a more concentrated butstill pump-able concentrate that may be subjected to further processingand/or disposal. In the context of this description, waste watersolutions containing contaminants are referred to as “raw water”.

The liquid reduction requirements dictated by the physicalcharacteristics of raw water have resulted in the development of a largerange of different types of evaporators over the years. Demands forenergy efficiency, minimized environmental impact, low capital cost andlow operating cost have driven evaporator development toward variousplant type configurations and equipment designs. In the design ofevaporation systems, numerous, and sometimes contradictory requirementshave to be considered, which may determine which type of constructionand configuration is chosen. The resulting principles of operation andeconomic performance between different designs may vary greatly. By wayof background, various design considerations may include:

-   -   Capacity and operational data, including quantities,        concentrations, temperatures, annual operating hours, change of        product, controls, automation, etc.;    -   Product characteristics, including heat sensitivity, viscosity        and flow properties, foaming tendency, fouling and        precipitation, boiling behavior, etc.;    -   Required operating media, such as steam, cooling water, electric        power, cleaning agents, spare parts, etc.;    -   Capital and collateral financial costs;    -   Personnel costs for operation and maintenance;    -   Standards and conditions for manufacture delivery, acceptance,        etc.;    -   Choice of materials of construction and surface finishes;    -   Site conditions, such as available space, climate (for outdoor        sites), connections for energy and product, service platforms,        etc.; and    -   Legal regulations covering safety, accident prevention, sound        emissions, environmental requirements, and others, depending        upon the specific project.

Based on the above, the applications and systems for evaporativeconcentration of raw water are diverse requiring design decisions beingbased on the deployment. For example, in some deployments, it isparticularly important that mobile water treatment plants are reliableand straight-forward to operate by onsite personnel.

One specific application that benefits from the use of an efficientmobile evaporative unit is the onsite processing of raw water generatedon and around a drilling rig that is produced from snow or rainaccumulations washing over equipment and/or other raw water produced orrecovered at the drilling rig lease.

Many environmental regulations prohibit raw water to be dischargeddirectly from the drilling lease surface area onto the surroundingground regions due to the level of contamination that may be present inthe raw water. For example, raw water may be contaminated with oils,soaps, chemicals and suspended particulates originating from thedrilling rig operations.

Normally, at a drilling rig, raw water must be collected in peripheralditches constructed as a first line environmental discharge barrier. Insome cases, the volume of raw water may become sufficiently great duringrig operations to inhibit the efficient operation of the drilling rig asthe volume of raw water interferes with the operation and movement ofequipment and personnel at the drill site. In these cases, the raw watermust be collected and/or removed to permit drilling rig operations tocontinue.

Often, in the absence of systems allowing on-site processing, the rawwater must be collected from the ditches, stored in holding tanks andeventually trucked to a remote processing center for processing anddisposal. As known to those skilled in the art, the collection, storage,transportation, processing and disposal of the raw water at the remotelocation can be very costly both in terms of actual handling andprocessing costs but also from lost time at the drilling rig.

In the past, there have been systems to reduce the liquid volume of rawwater by boiling off the aqueous phase of the raw water with a mobilewater evaporator/boiler. One such system is a diesel fueled boiler thatheats the raw water in a tank to boil raw water that may have beenpre-clarified through a series of settling tanks mounted on a skid basedevaporator system. The raw water is boiled in place to produce aconcentrated slurry as the aqueous portion of the raw water is boiledoff that settles near the bottom of an evaporator tank by gravity actingon an increasingly dense fluid. This bottom concentrate is periodicallyremoved from the evaporator/boiler system by various systems such asvacuum suction.

There are a number of inherent problems with existing evaporator systemsas listed and discussed below. These problems include:

-   -   Systems that must be operated in a batch process mode. In these        systems as any new addition of raw water to the bulk storage        tanks halts the evaporation process and requires reheating the        whole system before vaporization can resume;    -   The inefficient use of heat energy due to increasingly limited        thermal transfer from the heat source to the raw water, that may        be caused by:        -   a buildup of particulate and scale that coats various parts            of the system such as a heat exchanger, promoting increasing            heat loss out the heating system exhaust stack; and/or        -   the need to thermally heat un-separated, suspended            particulates in the raw water tank as the density increases;    -   Unnecessary fuel consumption, due to overall system        inefficiencies. In this case, fuel consumption may have to be        increased to meet target processing rates resulting in higher        costs to the operator and greater volumes of combustion        contaminants being discharged to the atmosphere;    -   Foaming and frothing of hot or boiling solutions over the sides        of the tank into the surrounding environment that may be        occurring in close proximity to personnel. Such problems may        also require the use of anti-foaming agents and system        supervision;    -   Frequent and time-intensive system cleaning;    -   Intensive and/or invasive onsite supervision to ensure the        evaporator system flow dynamics are within certain narrow        parameters to prevent automatic shut down and restarts;    -   Heating element damage from over-heating due to concentrate        accumulation on a heat exchanger; and    -   Soaps and oils present in the raw water that may cause surface        layering that inhibits the evaporation process.

A review of the prior art reveals that contaminated water evaporatorscan transfer heat to the contaminated water mass using a variety ofmethods to reduce the volume and weight of the concentrated water fortransportation and final disposal.

For example, Canadian Patent 2,531,870 issued Mar. 18, 2008 entitled“Evaporator System” and Canadian Patent 2,554,471 issued Sep. 16, 2008entitled “Self-Powered Settling and Evaporation Tank Apparatus”exemplify the current commercial prior art of ditch water evaporators.Typically these prior art systems are batch process systems where a tankis filled with the contaminated water and a heat source is applied nearthe bottom of the tank to transfer the heat to the total mass ofcontaminated water. The heat source can be any number of heating methodssuch as steam, electrical resistance heaters and/or hot gasses derivedfrom combustion or hot liquids. In these systems, the heat source mustelevate the temperature of the total contaminated water mass in the tankto a level before it can begin to boil off any of the water. Generally,these systems must also reheat the water mass each time additional wateris introduced into the reservoir thus significantly slowing the over-allevaporation process.

Over time, evaporation of the water from the tank with the addedcontaminated water increases the concentration of the non-evaporatedconstituents within the tank. While these systems will concentrate rawwater, it should be noted that as the concentration of the solids andother contaminants in the concentrated water increases, the likelihoodthat more contaminants from the evaporator will be carried from thesystem with the evaporated water vapor also increases.

In high temperature driven evaporators, because of the high temperaturedifferential needed to pass heat from the source through the heatingelement into the water, and because of the presence of chemical saltsand other contaminants, the heating element is subject to scaling,fouling and corrosion. Heating element coating creates a significantdecrease in efficiency within a very short time and requires frequentand intensive cleaning. Additionally, from the moment the heatingelement becomes coated (e.g. with scaling), which is almostinstantaneous upon system start up, heat is increasingly inhibited frompassing through the element into the water and thus is wasted out theflue stack. Complex control systems must sometimes be used with priorart evaporators to account for this fluctuation in exhaust gastemperature over time.

Additionally, when transferring heat through a heating element, theheating element surface area becomes key to the thermal transfer rateand efficiency. Typically the higher the evaporation rate required themore surface area is required on the heat element. Therefore thesesystems are not scalable on site. If they are to be scaled they must beremanufactured with different physical parameters.

Further still, in these systems, the increasing total solids massconcentration also decreases the efficiency of the evaporator due to theapplied heat being absorbed by any solids in the tank. As well, suchsolids also tend to line the tank surface and cover the heatingelements, tubes, and other components in the tank such as level sensorsand other monitoring instrumentation that will affect heat transfer andthe overall efficiency of operation.

Still further, another significant problem with various prior artsystems is the stratification of the waste water due to any soaps ororganic material that may be present in the waste water. The presence ofeither or both of these contaminants will often generate a surface skimor layer on top of the waste water that interrupts the water massevaporative process. To counter this problem, some past systemsincorporate significant complexities into a design to prevent and/ormitigate issues the effects of these contaminants in the waterevaporation process. Moreover, soap and/or organic materials can causesignificant foaming and frothing that can often result in overflowingthe heating tank and spillage onto the ground requiring expensiveclean-up operations and/or putting the operator at substantialenvironmental and safety risk.

A still further problem with various evaporators is particulate materialis not removed from the raw water prior to transferring the raw waterinto the evaporator tank thereby resulting in the need to remove theaccumulated solids frequently and/or, as noted above, the unnecessaryheating of particulate matter during evaporation. Drains are typicallyprovided in the tank to remove the sludge from the tank; however, thesludge must generally have a high water content in order to permit thesludge to flow through the drain.

Further still, sludge that remains coated on the tank and other elementsrequires periodic cleaning, usually with steam or water. The sludge andcleaning water, as a product of the cleaning process, must also behauled away which increases the total cost of operating the evaporator.

Examples of past systems also include those described in U.S. Pat. No.7,722,739, U.S. Pat. No. 5,259,931, U.S. Patent Publication No.2009/0294074, U.S. Pat. No. 5,770,019, U.S. Pat. No. 5,573,895, U.S.Pat. No. 7,513,972, U.S. Pat. No. 2,101,112, and U.S. Pat. No.6,200,428.

As a result, and in view of the foregoing, there has been a need forthermally efficient, continuous processes for waste water contaminantconcentration that can mitigate the various problems associated with theprior art systems.

In addition, there has also been a need for a system with the capabilityto concentrate waste water using waste heat generated from normaldrilling rig operations in order to provide further operational andefficiency advantages over systems in which a regular fuel supply isrequired.

Further still, there is also a need for a system that is alsosimultaneously effective in evaporating water and in removing combustionrelated soot, particulate and combustion chemicals from the heat sourceif applicable to the particular heating source. In other words,heretofore there has been no incentive for mobile treatment of fluegasses because there is generally no regulation on diesel engine exhaustto justify the cost of doing so. As such, and until regulation is set,the cleaning of these collectively large volumes of acid gasses will notoccur. While there are clear environmental benefits to cleaning engineexhaust at a well site, within the current regulatory framework, thiswill occur if the technology for cleaning exhaust is part of anothersystem. Accordingly, by marrying the technology for cleaning exhaustgasses with another use such as evaporating wastewater, there is aneconomic incentive to the operator to take this environmentallyresponsible action.

In regards to the emissions from drilling rig operations, there aregenerally over 2,000 rigs operating in North America with each oneconsuming on average approximately 3,000-9,000 liters per day of dieselfuel within the various power generating machinery. For example, for atypical 500 kW engine-generator set, each 500 kW engine, capable ofevaporating over 10 cubic meters of water per day, will exhaustapproximately 91-273 cubic meters per minute of acid gas exhaust intothe environment thereby polluting the environment and wasting the heatenergy contained therein. This equates to 95-285 billion cubic meters ofuncleaned acid gas discharge from all North American rigs every year.

Thus, there has also been a need for systems that can reduce the amountof exhaust contaminants that may be released to the atmosphere while atthe same time reducing the total volumes of contaminated waste waterthat requiring shipping and/or removal from a drilling rig site.

SUMMARY

In accordance with the invention, there is provided methods andapparatuses to concentrate waste water contaminants. In variousembodiments, the invention provides an apparatus and/or method for:

-   -   a) simultaneously concentrating waste water and cleaning the gas        stream used in its operation;    -   b) using waste heat energy generated by nearby equipment to        reduce new fuel consumption to concentrate raw water;    -   c) cleaning hot gas source(s) used to minimize the escape of        particulate, soot and combustion chemicals into the atmosphere;    -   d) that require minimal cleaning, due to pre-filtering of the        particulate from raw water;    -   e) enabling the direct interaction between the hot gas and raw        water thereby minimizing scaling and thermal losses;    -   f) having improved fuel efficiency    -   g) having onsite scalability;    -   h) capable of minimal start up times;    -   i) capable of quick onsite servicing and cleaning;    -   j) capable of continuous operation to minimize operation        downtime;    -   k) having less potential for an environmental hazard incident;    -   l) that is safer for personnel to operate and/or be in close        proximity to; and, m) having a simpler construction and        therefore less expensive to construct and operate.

In accordance with a first aspect of the invention, there is provided anevaporator for concentrating contaminants within raw water comprising: afirst tank for receiving and storing raw water; a raw water evaporatorincluding an insulated flue stack containing a packing material; and aheat source in operative communication with the insulated flue stack,the heat source for providing hot gas to the insulated flue stack at alower position wherein the hot gas rises within the flue stack throughthe packing material; a fluid distribution system for distributing rawwater to an upper region of the flue stack wherein the raw water flowscountercurrent to the hot gas through the packing material; and aconcentrated water collection system at a lower end of the insulatedflue stack for collecting concentrated raw water.

In further embodiments, the heat source is a hydrocarbon basedcombustion system operatively connected to the insulated flue stack andwherein the hot gas is a hydrocarbon combustion system exhaust gas. Invarious embodiments, the heat source is a flame burner.

In another embodiment, the concentrated water collection system is influid communication with the first tank.

In another embodiment, fluid from the concentrated water collectionsystem is in heat-exchange contact with fluid in the fluid distributionsystem for pre-heating fluid in the fluid distribution system beforedistribution over the packing material utilizing a tube-in-tube or othertype of heat exchanger.

In further embodiments, the systems for generating raw water surfacearea may include structured packing, random packing, a combinationthereof and/or spray or atomizing nozzle(s). The packing materials maybe in different layers, for example, where the random packing is beneaththe structured packing within the insulated flue stack.

In further embodiments, the system may also include a separation systemoperatively connected to the first tank for separating particulate andorganic material from the raw water before delivery to the first tank.In one embodiment, the separation system includes a screen operativelylocated above the first tank and a distribution manifold above thescreen wherein raw water is distributed over the screen by thedistribution manifold and passes through the screen to the first tankand wherein the majority of particulate matter does not pass through thescreen and is delivered to a second tank.

In another embodiment, components of the system such as each of thefirst tank, raw water evaporator, fluid distribution system andconcentrated water collection system are operatively configured to anyone of or a combination of a skid or trailer for delivery to a job site.The skid or trailer may also have a fuel tank for storage of fuel forthe heat source and/or the separation system.

In another embodiment of the invention, the heat source is engineexhaust from an adjacent engine and the evaporator includes insulatedpiping having a first end operatively connected to a lower end of theinsulated flue stack and a second end for operative connection to theadjacent engine.

In yet further embodiments, the heat source includes a heat source flueextending into the lower position of the insulated flue stack, the heatsource flue having a heat deflection system to radially deflect directheat from the heat source upon entry into the insulated flue stack. Theheat deflection system may also be a stool having an upper plate and atleast two hollow legs defining flue openings between the upper plate andheat source flue and wherein raw water impinging upon the upper platecan flow through the at least two hollow legs to the concentrated watercollection system.

In another embodiment, the system may also include an inner liner withinthe insulated flue stack wherein the inner liner is dimensioned todefine a fluid reservoir between the insulated flue stack and innerliner for collecting and receiving downwardly flowing raw water forproviding cooling and insulation to the lower position of the insulatedflue stack.

The system may also include a control system including at least onethermocouple for monitoring the temperature within the insulated fluestack and at least one pump for controlling the flow of raw water to thefluid distribution system.

In another embodiment, the system also includes an insulated gasexpansion chamber operatively connected to the insulated flue stack, theinsulated gas expansion chamber having dimensions to allow a highvelocity flame to fully develop.

In another embodiment, the random packing has a volume sufficient todissipate a hot gas temperature in a range of 300° C. to 1,500° C. to ahot gas temperature in the range of 50° C. to 1,000° C. before enteringthe structured packing.

In yet another embodiment, the evaporator includes a second insulatedflue stack adapted for configuration to an alternate heat source.

In yet another embodiment, where the system is adapted for configurationto an adjacent engine, the insulated flue stack and insulated gas pipinghave a total back pressure to the adjacent engine enabling the adjacentengine to operate at less than 100 cm water column of back pressure.

In another embodiment, the system simultaneously evaporates water andremoves particulate, soot and combustion chemicals from the gas stream.

In another aspect, the invention provides a method of evaporating rawwater comprising the steps of: providing heat in the form of hot gassesto a flue stack; distributing raw water within the flue stack by asurface area generating technique; causing the raw water to come intodirect contact with the hot gasses; and, collecting concentrated rawwater from the flue stack.

In further embodiments, the raw water is sourced from drilling rigoperations and/or around a drilling rig site.

In one embodiment, packing material is used to generate raw watersurface area within the flue stack.

In another embodiment, any one of or a combination of spray nozzles andatomizing nozzles are used to generate raw water surface area within theflue stack.

In various embodiments, raw water is flowed countercurrent to the flowof hot gases in the flue stack, concurrent to the flow of hot gases inthe flue stack or perpendicular to the flow of hot gases in the fluestack.

In another embodiment, the invention provides the further step ofpre-heating the raw water by placing the concentrated raw water in heatexchange contact with the raw water prior to distributing the raw waterto an upper region of the flue stack.

In another embodiment, the invention provides the further step ofcontrolling the temperature within the flue stack to minimize formationof scale on the packing material.

In another embodiment, the invention provides the further step ofcontrolling the temperature within the flue stack to minimize theformation of corrosive chemicals within the packing material.

In another aspect, the invention provides a method of removing soot,particulate matter and/or chemicals from diesel engine exhaustcomprising the steps of: providing diesel engine exhaust to a fluestack; distributing raw water within the flue stack by a surface areagenerating technique; causing the raw water to come into direct contactwith the diesel engine exhaust; and, collecting concentrated raw watercontaining diesel engine exhaust contaminants from the flue stack.

In a still further aspect, the invention provides a method ofsimultaneously evaporating raw water and removing soot, particulateand/or chemicals from flue gasses and/or engine exhaust comprising thesteps of: providing heat in the form of hot gasses to a flue stack;distributing raw water within the flue stack by a surface areagenerating technique; causing the raw water to come into direct contactwith the hot gasses; and, collecting concentrated raw water from theflue stack and wherein the hot gases can be sourced from flue gassesand/or engine exhaust.

The method may further comprise the step of preheating the raw water byplacing the concentrated raw water in heat exchange contact with the rawwater prior to distributing the raw water to an upper region of the fluestack.

The invention is described with reference to the following figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a right-hand isometric view of a concentrator system inaccordance with one embodiment of the invention;

FIG. 2 is a left-hand isometric view of a concentrator system inaccordance with one embodiment of the invention;

FIG. 3 is a right-hand isometric view of an evaporator assembly inaccordance with one embodiment of the invention;

FIG. 4 is a cross-sectional view of an evaporator assembly of FIG. 3 inaccordance with one embodiment of the invention;

FIG. 4A is a cross-sectional view of an evaporator stack of FIGS. 3 and4 showing further details of the evaporator stack in accordance with oneembodiment of the invention;

FIG. 5 is a right hand isometric view of an alternative evaporatorassembly in accordance with one embodiment of the invention;

FIG. 6 is a schematic cross-sectional view of an embodiment of aconcentrator system having an alternate evaporator assembly; and

FIG. 7 is a schematic cross-sectional view of an embodiment of aconcentrator system having two evaporator assemblies.

DETAILED DESCRIPTION

With reference to the Figures, various apparatus and methods forconcentrating raw water are described.

Overview

FIG. 1 shows a contaminant concentrator system (CCS) 10 mounted to anoilfield type skid 20. The CCS generally includes a tank system 30including first tank 60 and second tank 50, evaporator stack 110, filtersystem 40, fuel storage system 80, pump 70, burner 90, heat exchanger140 and flue gas expansion chamber 100.

The filter system 40 is mounted on tank system 30 and receives raw waterfrom a source for initial particulate separation in which particulatesare separated to second tank 50 and liquid raw water to first tank 60.Pump 70 pumps raw water from tank 60 through heat exchanger 140 to theinterior of the upper section of evaporator stack 110 where anevaporation process takes place as will be explained in greater detailbelow. Burner 90 provides heat to the evaporator stack through flue gasexpansion chamber 100 and the burner receives fuel from the fuel storagetanks 80. Concentrated raw water is removed from the evaporator stackthrough the heat exchanger and is returned to the first tank.

As shown in FIG. 2, further details of the system are described. A rawwater inlet pipe 46 is connected to an inline basket strainer 47 whichin turn is connected to flow line 48 and raw water distributor line 49for distribution of raw water to the filter system. The filter system 40includes a curved metal filter screen 44 which is held in place by sidesupport 42 (typically in 2 places) which is attached to tank 60. Secondtank 50 has a sloped bottom 52 and a discharge dump gate 54 for allowingparticulate materials to be removed from the second tank. First tank 60also has dump gate 62 for allowing discharge of contents of the firsttank.

Programmable logic controller (PLC) base controls 130 are shownconfigured to the side of raw water tank 60 and is configured to athermocouple 122 within the evaporator stack and the pump 70.

Evaporator Stack

With reference to FIGS. 3, 4 and 4A, components of the evaporatorcircuit are described. As noted above, pump 70 is connected to firsttank 60 by suction line 72 that draws water from the first tank that isthen pumped through discharge line through heat exchanger 140 to a rawwater distribution system 74, 76 at the upper portion of the evaporatorstack. In a preferred embodiment, the suction line includes a flexibleintake hose configured to a float that draws raw water from a depth justbelow the liquid surface within the first tank. Burner 90 is connectedto the interior of combustion gas expansion chamber housing 100 which isconnected to the interior of evaporator stack 110 as shown in greaterdetail in FIG. 4.

FIGS. 4 and 4A illustrates the cross-sectional interior of theevaporator stack of FIG. 3. The evaporator stack 110 includes an outerwall 110 a and an inner wall 112 defining an annular space containinginsulation 111. The evaporator stack is mounted on the upper surfaces ofthe burner assembly 100 around flue 117 that projects a short distanceinto the evaporator stack. The flue operatively supports collector stool115 that is positioned over the flue. The collector stool has a topsurface 115 a, hollow side legs 15 b and lip 115 c that collectivelydefine side openings allowing exhaust gases from the burner to enter theevaporator stack 110. The lip 115 c extends upwardly from top surface toprevent raw water 125 within the evaporator stack from entering theexpansion area 03.

As shown in FIG. 4A, an inner packing support pipe 116 is providedinside the inner wall 112 at a distance that defines annular space 119.The inner packing support pipe 118 supports packing material above thecollector stool and below the raw water distribution system. Asexplained in greater detail below, packing materials preferably includesa random packing material 114 and a structured packing material 113. Aconcentrated raw water outlet 120 is provided that is in fluidcommunication between the lower space 123 and the exterior of theevaporator stack.

In operation, pre-heated raw water from the heat exchanger is pumpedfrom the fluid distribution system 74, 76 where the raw water flowsdownwardly through the interior of the evaporator stack 110 over thestructured packing 113 and random packing 114 and countercurrent torising hot gas 124 from the burner. As the raw water is falling, it issubjected to evaporation and hence concentration and the burner exhaustwith water vapour is released to the atmosphere through the top of theevaporator stack. After passing through the packing material, the rawwater will fall to top surface 115 a of the collector stool 15,downwardly through legs 115 b where it will flow from the evaporatorstack through outlet 120.

In addition, the falling raw water will also flow along the interiorwall 112 and enter and fill annular space 119 where it will be subjectedto heating and gentle boiling. Advantageously, the water-filled annularspace will contribute to insulating against thermal losses from thestack as well as cooling the inner surfaces of the inner packing supportpipe. As raw water is boiled out of the annular space 119 or otherwiseoverflows the annular space, additional raw water will flow in, hencemaintaining a degree of circulation within this space. Generally, thedimension of the annular space should be controlled to ensure thatexplosive boiling within the space does not occur.

The drain pipe 120 is connected to heat exchanger 140 where hotconcentrated raw water 126 is drained from the lower end of interiorspace 123 into the heat exchanger interior space 142 and to the firsttank 60.

It should also be noted that other designs could incorporate eitherperpendicular or concurrent flow within the evaporator stack to effectevaporation.

Burner

As shown in FIG. 4, burner 90 is connected through flow connector 102into the interior of gas expansion chamber 100 with gas expansion area103. Gas expansion area 103 is connected to interior space 123 throughflue 117. Insulation 101 is located within gas expansion chamber 100 toinsulate the gas expansion chamber 100.

Burner 90 is a typical a forced air burner (e.g. a diesel burner)drawing fuel from tanks 80. Fuel and air are mixed and atomized withinthe combustion chamber to produce a high heat density and high velocityflame.

Importantly, as shown in FIGS. 5 and 6, the heat source can beconfigured to other heat sources including various types, models andsizes of forced air/fuel burners and/or the exhaust generated by analternate heat source such as engine. Examples of alternate heat sourcesat a drilling rig include electrical generator engines that run variousequipment such as mud pumps. The capture of heat exhaust from an enginecan be captured and flowed to the system through an insulated hose 150as a standalone heat source. As shown in FIGS. 5 and 6, an insulatedhose 150 is connected to evaporator stack 110 through insulated flowline 152 by coupling 151.

A further embodiment is shown in FIG. 7, in which a duel system isprovided. In this embodiment, the system includes two insulated fluestacks 110 each configured for a different heat source thus providingthe operator with the opportunity to choose the most efficient orcombined heat source for a given installation. In the event thatadjacent engines are not present to enable the utilization of waste heatfrom the adjacent engine, the system could be changed over to the dieselburner heat source. As both insulated flue stacks draw water from thesame first tank, the change-over can be completed quickly. Theembodiments of FIGS. 6 and 7 are configured to process raw water 125.

An effective diesel burner is a Beckett Model CF-1400 diesel burnercapable of supplying approximately 900,000 Btu/hr resulting in theprocessing of approximately 9 cubic meters per day of raw water. Withthe optimized air settings on the burner of approximately 30 cubic feetper minute (CFM) intake air per gallon/hr of diesel consumed will createa gas temperature of approx 800° C. which is cooled to approximately 75°C. as it exhausts the evaporation stack 110 as exhaust saturated withwater vapor.

Filter System 40

As noted above, raw water is initially pumped through piping 46 to andthrough an inline basket strainer 47 to remove large particulatecontaminants greater than approximately one quarter of an inch indiameter.

The raw water is pumped through piping 48 from the inline basketstrainer 47 to distributor manifold 49 where the raw water is dischargedevenly across the top of screen filter 44. The screen filter 44 ispreferably a curved v-wire screen designed to remove suspendedparticulate down to approximately 25 microns. Other types ofpre-filtering system that can be substituted for screen type filter 44as known to those skilled in the art include but are not limited tofilter systems such as electric powered self cleaning (self purging)filters, filters that trap particulate, hydro-cyclones and centrifugetype particulate separators. The screen filter 44 is design to separateand direct the separated particulate into second tank 50 where the wastematerial is stored for periodic removal.

Second Tank

The second tank 50 has a sloped bottom 52 to passively direct the wastematerial to dump gate 54 which makes the cleaning process fast andefficient for the operator.

First Tank

Raw water passing through screen filter 44 flows into first tank 60. Thefirst tank has sufficient volume such that it serves as both a storageand settling tank wherein at normal operational flow rates, the rawwater in the first tank will settle and stratify due to the absence ofsignificant fluid circulation that would otherwise mix the tankcontents. Operationally, this will improve the efficiency in that thesettling of denser liquids, and particles (including salt precipitates)will minimize the amount of heat used to heat suspended particles.

Operational and Design Considerations

Generally, for every 100,000 Btu/hr of hot gas stream, a properlyinsulated system should evaporate approximately 1 cubic meter of waterper day. Thus, for a given 900,000 Btu/hr input, the system shouldevaporate approximately 9 cubic meters of water per day. As it is knownthat for 3.8 liters of diesel consumed, 140,000 Btu/hr heat energy isgenerated, therefore a 900,000 Btu/hr system will consume approximately24.6 liters/hour (LPH) of diesel. This equates to approximately $50 indiesel consumption per cubic meter of water evaporated. This compares totypical prior art boiler evaporators where the cost of evaporation istypically in the range of $150 in diesel per cubic meter of waterevaporated because of thermal losses and system inefficiencies.

Similarly, using the waste heat from a diesel engine would accomplishthe same evaporation for an effective rate of $0 in extra fuel cost percubic meter of water evaporated. As such, the fuel savings are highlyattractive to potential operators, especially as the use of exhaust heatin the system has the added benefit of reduced acid gas emissions fromdiesel exhaust that would otherwise be discharged into the environmentdue to the scrubbing effects within the evaporator stack. That is, thesystem can be highly effective in removing particulates, soot and othercombustion chemicals from the gases within the evaporator stack.Accordingly, the system can be operated as an evaporator, an exhaust gascleaning system (effectively without or with minimal evaporation) or asa combination of both.

Furthermore, the particular type of raw water effluent sourced fromdrilling operations can further enhance the ability of the system toclean exhaust gasses. For example, boiler blowdown, a type of chemicallycontaminated waste water produced during drilling rig operations, isnormally kept at a high pH by rig personnel. This is done by addingcostly alkaline chemical additives to water used in the rig boilersystem so as the alkaline water/steam circulates though drillingequipment scaling effects are minimized. Accordingly, the boilerblowdown is highly contaminated water, and because of its alkalinity canbe a highly effective effluent for neutralizing acid gasses or engineexhaust. Thus, as a neutralizing agent, this alkaline solution canassist in preventing acid gasses from escaping the flue stack and is,therefore, another example of how the present invention can make use ofa readily available, expensive and typically a waste product, with noadditional cost to the operator as its cost has already been paid for inother drilling rig operations. Therefore, the chemical nature of the rawwater to be evaporated can come in a form that assists the system in asecond or standalone function of cleaning the gasses used to evaporatethe raw water.

Furthermore, if desired the system can be operated at a higher firingrate, resulting in faster water evaporation in a given timeframe bysimply increasing the pressure of the fuel pump, changing the nozzlewith one of more capacity and/or increasing the air intake setting onthe burner. As known to those skilled in the art, scalability isdesirable because in times of high rainfall, the operator will oftenneed to increase the process rate. Importantly, the subject systemallows a rapid processing rate increase rate simply by increasing flowrates and burner temperatures without the delay or the off-siteremanufacture typical in the prior art.

Further, using the exhaust heat from a engine/generator system alone orin combination with a forced air fuel burner, typically ranging from 500kWh to 1,000 kWh (1.5M-3M Btu/hr) for use on a drilling rig for example,would provide sufficient heat energy to process an additional 10 to 20cubic meters of raw water per day with no new cost to the operator, asthe cost of the combusted fuel has already been paid for in otheroperations.

Importantly, the use of waste engine exhaust heat requirescontrol/monitoring of the backpressure being exerted on the engine'sexhaust system. In a typical operation, this is typically 100 cm ofwater column (WC). The subject system is designed to operate between 1-2cm of WC due to the lack of significant flow resistance within therandom packing, structured packing, a combination of both and/or sprayor atomizing nozzle flow path.

The methods of generating large amounts of raw water surface area can beimportant to the efficient rate of thermal mass transfer of heat fromthe hot gas into the raw water for the purpose of evaporation. Morespecifically, random packing rated for above 150 m²/m³ with 75%-98% voidspace is preferred and structured packing with 500 m²/m³ with 98%+/−voidspace is preferred for use with a 500 kWh engine having an exhaust flowrate of approximately 3,200-3,400 CFM with a temperature of 500-700° C.,or other fuel combusting device such as a diesel burner producing gassesover 800° C. As an alternative of generating large amounts of raw watersurface area and distribution within the flue stack, atomizing nozzlesor spray nozzles can be used alone or in conjunction with packingmaterial.

The acidic nature of the gas stream should also be considered to avoidcorrosion, pitting and weakening of materials used in the apparatus dueto the high temperatures involved. For example when sulfur oxides in thediesel gas stream react with raw water, diluted sulfuric acid (liquid)is formed which in turn can react with different chemicals within thewaste water. As a result, ceramic random packing is the preferred choicefor a surface area matrix for the hot gas to contact first because ofits corrosion resistance and high heat tolerance. By flowing the hot gasthrough the random packing first, the gas is cooled prior to enteringthe structured packing thus preserving the structured packing life, asstructured packing is generally made from thinner alloys. A 10″ layer ofrandom packing is sufficient to reduce the gas temperature fromapproximately 800° C. to 150° C. For the structured packing HastelloyC22 is preferred for its resistance to oxidizing corrosives, stresscorrosion and thermal stability at temperatures ranging from 650°C.-1,040° C. Stainless Steel can be used as well, but will usually needmore frequent replacement.

Scale buildup poses another problem as soot and particulate plus thesalts from chemical reactions are concentrated into a reduced watervolume in the column. These chemical and heat issues are controlled bymaintaining sufficient flow of concentrated water returning to the firsttank. Because the concentrated raw water is flowing through a heatexchanger the heat is retained in the column. This is important toprevent and/or control scaling as the water feed rate can be increased,and although the ratio of evaporation to feed water changes, the overallevaporation rate remains substantially constant. As a result, the systemhas the benefit of having more water flowing as concentrated raw waterand therefore can be used to maintain a cooler temperature within thecolumn with limited scale buildup.

To further minimize maintenance requirements of periodically removingscale, the preferred packing configuration of random packing adjacentthe burner and structured packing in the upper portion of the evaporatorstack, provides cost advantages as the majority of scaling will occur inthe lower regions of the evaporator stack and the random packing isgenerally cheaper to replace than the structured packing if scalingnecessitates cleaning and/or replacement. In another configuration, rawwater sprayed from nozzles beneath the packing material countercurrentdirectly into the gas stream, can also assist in limiting scaling whilecooling the gas prior to it entering a packing material.

Burner 90 can be augmented with an additional fan to force additionalair into the burner system to provide an excess of dry air to ensure theexhaust fluid will not fully saturate.

The discharge plenum 102 and hot gas expansion chamber 103 are formed asa cavity within a high density insulation material 101 held in place bycombustion expansion chamber housing 100. The high density insulationmaterial 101 provides sufficient insulation to ensure a maximum amountof heat energy generated by the combustion process is retained withinthat portion of the hot gas circuit. In one embodiment, approximately 9lbs/ft³ folded ceramic blanket anchor lock insulation modules are usedwhich are rated to have over 800° C. on the hot face while keeping thecold face below 35° C. with a low thermal conductivity rating. Thisensures the water in the tank is close to ambient temperature and theheat stays in the expansion chamber, heat exchanger and evaporatorsystem.

An additional benefit of this choice of insulation modules is that thefolded blanket modules compress against one another as they are anchoredto the walls of the combustion chamber so repeated firing in the chamberwill not shrink the insulation allowing heat to penetrate the insulationas is the case using traditional ceramic insulating fiber board.Further, this style of ceramic blanket module will not become brittle,as will traditional fiber board from repeated firing. This is beneficialfor a mobile system that will be loaded and unloaded from transporttrucks, driven over non-paved roads and subjected to extreme vibrationsuch as mobile units delivered to remote drilling sites.

Raw water is drawn into and through suction line 72 from raw water tank60 by the action of pump 70. Although there are a great range of pumpsthat can be used, the preferred embodiment would be a vertically mountedcentrifugal pump. Unlike other pumps, because there are no seals asbarriers to flow, the centrifugal pump will allow the water in the pipesof the system to self-drain when the pump is shut off (provided the linerequired to be so drained is above the pump and the water level in thestorage tank 60 is below the pump). This is beneficial particularly whenthe system is operated in sub-zero temperatures. In addition, a selfdraining system design reduces the possibility of feed lines freezingand bursting when the system is not in operation, thus improvingreliability and other operational costs. Alternate pumps styles couldalso include positive displacement pumps and diaphragm pumps with anassociated glycol reservoir to fill the water lines upon systemshutdown.

Other heat exchangers can be used in place of the preferred tube intube, for example a plate heat exchanger. In the preferred embodiment,because gravity is acting on the concentrated water returning to thetank, the outer tube 141 should be large enough to allow complete freeflow of discharge liquid back into tank 60. Thus, with sufficient volumein space 142 the concentrated water will preferentially flow only in thebottom area of space 142. This means that tube 74 should be placed atthe bottom of space 142 in order to facilitate the transfer of the heatin the concentrated raw water stream through the surface area of thefeed line 74 and into the feed water. By way of example, for a systemthat evaporates 9 cubic meters of water per day, a 12 meter heatexchanger is sufficient and to save space is helically wound next to theriser but also to promote the downward flow particularly in the event ifthe skid is not level at a job site. This method allows the concentratedraw water, (typically about 98° C.) to give off its sensible heat to thefeed raw water. The concentrated raw water is thereby cooled to within afew degrees of the feed water before being discharged back into thefirst tank hence preserving heat in or adjacent to the evaporator stack.

The feed water pumping rate depends on the desired evaporation rate.Typically, the system would be set to pump a feed rate approximately 20%or more above the desired evaporation rate as determined by the Btuinput of the chosen hot gas source.

The hot gasses distributed radially around the collector stool 115 flowfirstly into and through random packing 114 where the hot gasses aredistributed through the volumetric space presented by the random packing114 and thereby comes into contact with raw water flowing through therandom packing 114. The hot gasses are subjected to a 1^(st) level ofcounter flow heat transferred to the raw water. This first interactionof the gas and water in the random packing allows for scaling,significant cooling of the gas and chemical reactions to take place inthe less expensive, thermally stable (at high temps) and corrosionresistant layer. It is also in this region that the sulfur oxides in theexhaust gasses, soot and particulate are predominantly removed from thegas stream and allowed to flow out drain 120 with the concentratedreject water. Adding to this function in the hot gas flow region is thewater spilling over 118 from space 119 directly into the annular spacebetween collector stool 115 and wall 119 which further adds to the gascooling effect.

The hot gasses passing though the random packing 114 then pass into andthrough structured packing 113 where the hot gasses are subjected to a2^(nd) level of counter flow heat transfer to the raw water flowingvertically downward through the structured packing 113. This structuredpacking layer, with a much higher surface area to volume ratio,completes the evaporation process bringing the gas and water vapormixture to a temperature of approximately 75° C. as it is dischargedinto the atmosphere.

As a result, the heating of the raw water by forcing the directinteraction of the hot combustion gasses and raw water allows for ahighly efficient thermal mass transfer. Other types of materials andconfigurations can be used for effecting the interaction between the hotcombustion gasses and the raw water with varying levels of efficiencyincluding but not limited to machine shop cuttings, mushroom capbubblers, spray or atomizing nozzles, random packing and structuredpacking.

Various means can be used to distribute the raw water over the top ofthe structured packing 113, such as spray nozzles, atomizing nozzles,gravity distributor and a “T” type distributor. Those systems thatminimize pressure drops and entrainment are preferred.

If dry vapor discharge is required, a mist eliminator (not shown) can beinstalled within the evaporator stack 110 to trap entrained liquiddroplets from being carried in the exhaust vapor thereby providinggreater dwell time for the liquid droplets to vaporize and be passedinto the atmosphere as pure vapor.

The control of the system is enabled by a minimal number of controlpoints. A Programmable Logic Controller (PLC) or Simple Logic Controller(SLC) unit provides the necessary system to measure the input ofspecific temperature levels of the exhaust fluids proceeding from theinterior of the evaporator stack 110, to ensure startup proceduresoperate correctly. In the preferred embodiment the thermocouple servesonly to signal system shutdown if either the pump or the burner stopoperating as sensed by a significant increase or decrease in temperatureduring operation. In another embodiment the thermocouple is designed toanalyze the information and generates a control signal to adjust thevolume of raw water feed into the system which will in turn modulatesthe exhaust temperature (this method of sensing may only be needed inthe absence of the heat exchanger in the system). A single thermocouple122 placed within the interior space formed by interior tube surface 112provides the operating temperature within the interior space defined byinterior wall 2. The PLC in turn adjusts the speed of pump 70 tomodulate volume of raw water being feed into the system. By adjustingthe raw water feed as a function of the amount of heat being generatedat any given time, the optimum evaporation can take place. Themonitoring and adjustment of temperatures within the interior of theevaporator stack 110 is thereby used to effectively maximize thevaporization of the raw water. The thermocouple 122 senses thetemperature of the fluid vapor in the exhaust gasses and when thetemperature varies from approximately 75° C. a variable frequency drive(VFD), controlled by the PLC will adjust the pump 70 speed to modulatethe evaporation system operation to generate fluid exhaust temperatureswithin the optimum range for the desired output. Generally, once theparameters are set, the system will not require any further attentionand will operate automatically within the preset ranges.

Although the invention has been described and illustrated with respectto preferred embodiments and preferred uses thereof, it is not to be solimited since modifications and changes can be made therein which arewithin the full, intended scope of the invention as understood by thoseskilled in the art.

What is claimed is:
 1. An evaporator for vaporizing raw water fromoilfield operations and concentrating contaminants within the raw water,where the raw water contains oil, salt and particulate contaminantscomprising: an internal combustion engine configured to provide a hotgas source; a raw water evaporator having a stack and a flue connectedto the hot gas source and wherein the stack is operatively positionedover and surrounding the flue; a raw water distribution systemconfigured to distribute raw water within the hot combustion gas withinthe stack to increase raw water surface area; a control system and pumpoperatively connected to the raw water distribution system, the controlsystem and pump operable to distribute a flow rate of raw water throughthe raw water distribution system within the stack while maintaining rawwater flow sufficient to minimize scaling within the raw waterevaporator during operation to enable optimum evaporation of waterwithin the flue; and a concentrated raw water collection systemconnected to the stack for collecting concentrated raw water from thestack and recirculating raw water to the stack.
 2. The evaporator ofclaim 1, further comprising a first tank operatively connected to theraw water evaporator, the first tank for receiving and storing raw waterand concentrated raw water from the raw water evaporator.
 3. Theevaporator of claim 2, wherein the raw water has a liquid surface withinthe first tank, further comprising an intake configured to a float thatallows raw water to be drawn from a depth below the liquid surfacewithin the first tank for delivery to the raw water distribution system.4. The evaporator of claim 1, wherein packing material is used togenerate raw water surface area within the stack and wherein the packingmaterial includes any one or combination of structured packing andrandom packing.
 5. The evaporator of claim 1, further comprising one ofor a combination of spray nozzles and atomizing nozzles to generate rawwater surface area within the stack.
 6. The evaporator of claim 1,wherein the hot combustion gas enters the raw water evaporator at alower position and the hot gas rises within the stack through thedistributed raw water and wherein the stack includes a drain preventingraw water from entering the flue.
 7. The evaporator of claim 2 wherein,the concentrated water collection system is in fluid communication withthe first tank and includes a heat exchanger wherein concentrated rawwater from the concentrated raw water collection system is inheat-exchange contact with raw water in the raw water distributionsystem, the heat exchanger for pre-heating raw water in the raw waterdistribution system before distribution within the stack.
 8. Theevaporator of claim 2, wherein each of the first tank, raw waterevaporator, raw water distribution system and concentrated raw watercollection system are operatively configured to any one or a combinationof a skid and trailer for delivery to a job site.
 9. The evaporator ofclaim 1, wherein the engine has an exhaust gas temperature in a range of300° C. to 1,500° C. and the raw water evaporator includes insulatedpiping having a first end operatively connected to the flue and a secondend connect to the adjacent engine and where backpressure on the engineis controlled to 1-2 cm water column.
 10. The evaporator of claim 1,wherein the flue has a heat deflection system to radially deflect directheat from the hot gas source upon entry into the stack.
 11. Theevaporator of claim 1 further comprising an inner liner within the stackwherein the inner liner is dimensioned to define a fluid reservoirbetween the stack and inner liner for collecting and receivingdownwardly flowing raw water for providing insulation and cooling to alower position of the stack.
 12. The evaporator of claim 1, wherein thecontrol system includes at least one thermocouple for monitoring thetemperature within the stack.
 13. The evaporator of claim 1, furthercomprising a second stack adapted for configuration to an alternate hotgas source.
 14. The evaporator of claim 1, wherein the engine is adiesel engine and the raw water evaporator simultaneously vaporizeswater and removes particulate, soot and combustion chemicals from thehot combustion gas.
 15. The evaporator of claim 1, wherein the engine isconfigured to supply heat at a rate of 1.5M-3M Btu/hr.
 16. Theevaporator of claim 1, wherein the flue stack and piping have a totalback pressure to the engine enabling the engine to operate at less than100 cm water column of back pressure.
 17. The method of claim 1 whereinthe raw water evaporator is configured to exert an additionalbackpressure on the engine of 1-2 cm water column.
 18. A method ofvaporizing raw water from oilfield operations and concentratingcontaminants within raw water where the raw water contains oil, salt andparticulate contaminants comprising the steps of: a. providing heat inthe form of hot gases to a stack operatively connected to a flue wherethe hot gas is a combustion gas from an internal combustion engine andthe stack vaporizes and vents vaporized water to the atmosphere; b.distributing raw water within the hot combustion gases within the stackby a surface area generating technique; c. causing the raw water to comeinto direct contact with the hot gasses within the stack; d. monitoringat least one temperature within the stack; e. controlling the flow ofraw water within the stack while maintaining continuous raw water flowsufficient to minimize scaling within the stack during operation; and,f. collecting concentrated raw water from the stack within a holdingtank and recirculating concentrated raw water from the holding tank tothe stack.
 19. The method of claim 18, wherein the raw water is allowedto at least partially stratify within the holding tank prior todistribution within the stack, and wherein the raw water has a liquidsurface within the holding tank and the raw water distributed within thestack is drawn from a depth below the liquid surface.
 20. A method ofsimultaneously a) concentrating contaminants within raw water, where theraw water is from oilfield operations and contains oil, salt andparticulate contaminants and b) removing soot, particulate and/orchemicals from flue gases and/or engine exhaust comprising the steps of:a. providing heat in the form of hot gas to a stack operativelyconnected to a flue where the hot gas is a combustion gas from aninternal combustion engine; b. distributing raw water within hotcombustion gases within the stack by a surface area generatingtechnique; c. causing the raw water to come into direct contact with thehot gasses; d. monitoring at least one temperature within the stack; e.controlling the flow of raw water within the stack while maintaining rawwater flow through the stack sufficient to minimize scaling within thestack during operation; and f. collecting concentrated raw water fromthe stack within a holding tank and recirculating raw water within thestack.